`git-cheat-date` – A custom git command for conveniently updating both the committer date and the author date

git-cheat-date

#!/bin/bash
# Usage: git cheat-date

git rev-parse || exit $?

if [[ $1 == "-q" ]]; then
	if_quiet="-q"; shift
else
	echo "Replacing committer date..."
fi

# Stash if the index contains uncommitted changes.
if ! git diff-index --cached --quiet HEAD --ignore-submodules --; then
	git stash $if_quiet
	did_stash=1
fi

export GIT_COMMITTER_DATE="$([[ $1 ]] && echo "${!#}" || git log -1 --date="iso" --format="%ad")"
git commit $if_quiet --amend --no-edit --date="$GIT_COMMITTER_DATE"

if [[ $did_stash = 1 ]]; then
	git stash pop --index $if_quiet
fi

See also, https://gist.github.com/jasonsparc/736ef0e0bcac7025addf8a4ac3e1cc16